The present invention relates to an apparatus and a method for measuring fixing forces for fixing states of various members in an electric machine.
A generator as one of measurement objects includes a rotor and a stator. A change in a magnetic field generated by rotation of the rotor is converted into an electric energy by the stator. The stator has a structure in which a coil is inserted into a slot of a core formed by laminating silicon steel plates one upon another, and fixing is carried out under a pressure by an insulating member.
For a fixing method under a pressure, a structure is adopted in which a corrugated plate spring and a wedge as a plate-like member are stacked on top of each other above a coil, and the corrugated plate spring is pinned down by the wedge while the corrugated plate spring is compressed, thereby fixing a coil conductor.
In such a fixing structure, it is necessary to maintain and manage the coil in a predetermined fixing state under a pressure. In the generator having the coil fixing structure described above, after a lapse of predetermined time (usage period), the wedge is inspected for the fixing state thereof. Also, if there is the loose in the fixing state of the wedge, then, for recovery of an applied pressure, replacement, adjustment, and maintenance of the wave-like spring and the wedge are carried out. Until now, the inspection and judgment for the fixing state of the coil has relied on an organoleptic examination in which the fixing state of the coil is judged based on sounds and vibrations. In this case, a person strikes the wedge with a hammer for examination, thereby generating the sounds and vibrations.
A method described in Japanese Patent No. 3 973 203 is known as an attempt to quantify the organoleptic examination. With this method, a member is excited, and a vibration response is detected and is compared with plural vibration responses previously recorded, thereby estimating a pressure applied to a wedge. Also, this method includes a step of obtaining a center of an energy band of spectra as a spectral analysis for the comparison with the vibration response. In addition, Japanese Patent No. 4 456 723 describes a method of quantitatively judging a degree of soundness of concrete based on a hammering sound from the concrete. This method is such that a surface of the concrete is hit by an impulse hammer, and a known quantity of hammering input and a hammering sound propagated through the concrete are both analyzed, thereby judging the degree of soundness of the concrete.